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# Experiment Assignment Help

## Introduction

The rate of reaction can be defined as how fast the reactants are consumed or how fast the products are formed. The reaction rate is directly proportion to the concentration of reactants. The rate of reaction depends on the following factors: (Meacham, B. (2019))

1) Concentration

2) Temperature

3) Catalyst

4) Order of Reaction

As concentration of reactant increases the collision between the molecules increases and thus rate of reaction increases. Similarly, as the temperature increases the kinetic energy of the molecules increases thus increasing the number of collisions per second leading to the increase in the rate of reaction.Thus, for the current experiment temperature must be controlled. Catalyst if induced in the experiment can lead to the increase in the rate of reaction.

Order of the reaction and the reaction constant k also plays an important role in determining the rate of reaction.

2HCl(aq) + Na2S2O3(aq) → 2NaCl(aq) + SO2(aq) + S(s)↓ + H2O(l) (UKEssays.com. (2009).

The reactants in this experiment are: HCl (Hydrochloric acid) & Na2S2O3(Sodium thiosulphate) The products in this experiment are: SO2 (Sulphur dioxide), NaCl (Sodium Chloride), S(Sulphur) & H2O (water) Firstly, the reactants form a transparent solution and after some time as the reaction proceeds the Sulphur molecules are formed which makes the solution cloudy. Thus, the rate of reaction can be determined by determining the time taken for the cross placed below the beaker to disappear completely. Thus reaction rate is inversely proportional to the time required for the cross mark to disappear.

## Procedure

### Materials Required

The following materials are required for the experiment:

1) 5 conical flasks with label A, B, C, D & E.

2) 0.25 M Na2S2O3 or can be prepared by diluting higher molar concentration solution.

3) HCl solution

4) Distilled water

5) Stopwatch

6) Pipette

Method

1) Take the 5 conical flasks with label A, B, C, D & E.

2) Rinse them properly with distilled water.

3) Draw a large ‘X’ mark on a piece of paper.

4) Using 0.25M Na2S2O3 prepare 5 solutions in each of the beaker with varying concentration such as:

5) Place beaker A on top of the X mark.

6) Add 10 ml of 1M concentration HCl into beaker A and start the stopwatch immediately.

7) Record the time required for the X mark to disappear.

8) Repeat the same for the remaining beakers.

### Safety

The following risk are involved in the experiment:-

1) HCl is used in high concentration and can be corrosive to skin and eyes.

2) S02 is produced in the reaction which is irritant to skin and eyes.

3) Na2S2O3 can cause hazards to body tissue.

The follow safety procedures need to be followed:-

1) Make sure to rinse the apparatus properly.

2) Wear goggles and hand gloves for safety.

3) Wear chemical aprons while conducting the experiment.

4) Use a stopwatch properly to get accurate results.

## Variables

### Independent variable

The concentration of sodium thiosulphate is an independent variable.The concentration data ranges from 0.25-0.05 and has the following data points 0.25,0.20,0.15,0.10,0.05.

### Dependent variable

The dependent variable is rate of reaction or time which can be estimated using stopwatch. The time required for the cross mark to disappear.

### Controlled variable

The controlled variables for this experiment are temperature and the concentration and volume of HCl.

Hydrochloric acid used in the experiment has a constant concentration where else addition of distilled water into the Na2SO3 solution reduces its concentration.

## Results

The following results are obtained:-

The following graphs are obtained:-

## Discussion

Concentration of Na2S2O3 was graphed properly with both reaction time and reaction rate in order to understand the reaction kinetics properly.

From figure 3 it can be clearly seen that the equation obtained is:

y=0.1716x-0.0018

Where y= reaction rate

X = Conc. of sodium thiosulphate solution

The equation obtained is a linear one thus in align with our theory stated above. Thus, we can conclude that the rate of reaction varies directly with the concentration of the reactants which in our case was Na2S2O3.

The results obtained above were highly accurate and most of the data points fit completely into the curve. There were very few outliners in the experiment. The methodology was also good and thus the results obtained are also good.

The materials used for the experiment were rinsed properly and were in a suitable condition for the conduction of experiment. The results obtained are more sort of error free but the possible cause of such small error could be human error (i.e. stopwatch not properly utilized) and error in the measurement of reactants. Other factors such as temperature could also lead to errors.

## Conclusion

The experiment was conducted as per the standard norms. The experiment had some errors but was good enough to help us in understanding the effect of concentration on the rate of reaction. The following improvements could be suggested for the better conduction of the experiment: -

1) Repetition of the experiment several times for better and accurate results.

2) Experiment should be conducted in a temperature-controlled area.

3) Using a stopwatch with having a small least count will lead to accurate results.

## References

1) Sodium Thiosulphate and Hydrochloric Acid. [online] Available at: https://www.ukessays.com/essays/chemistry/test-affected-by-changing-the-concentration.php.

2) Meacham, B. (2019). Investigating the Effect of Concentration on Reaction Time. [online] Chemical Education Xchange. Available at: https://www.chemedx.org/blog/investigating-effect-concentration-reaction-time.

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